The present invention refers generally to heat exchangers and, more specifically, to tube and fin-type evaporators for use in major appliances such as refrigerators.
Refrigerators typically include one or more enclosures or chambers for storing food or other articles to be cooled or frozen. The refrigerator housing about these enclosures includes two intersecting fluid circuits: a refrigerant circuit and a cooling air circuit. The refrigerant circuit includes a compressor, a condenser and an evaporator with tubing between these elements to permit the flow of the refrigerating fluid, Freon-12, for example. The cooling air circuit typically includes passageways for air to travel between the enclosures and the evaporator and an impeller, such as a fan, for causing the air to flow within the circuit. These two circuits intersect at the evaporator, which serves to enable the transfer of heat from the cooling air to the refrigerating fluid.
Evaporators for refrigerators typically include a tube and fin-type arrangement wherein a serpentine tube containing the refrigerating fluid passes through the evaporator, with air paths over the serpentine tube defined by the longitudinal length of these fins. One example of such a tube and fin-type evaporator is shown as element 16 of FIG. 3 in U.S. Pat. No. 3,745,786, issued Jul. 17, 1978 and also owned by the assignee of the present invention.
It has been found to be desirable to increase the efficiency of such tube and fin-type evaporators and to decrease the size of the evaporator. An evaporator can be made more compact by, for example, increasing the density of the fins and/or by increasing the inlet flow velocity of the cooling air. However, if fin density is increased, the normal frost build up on the fins can clog and close the flow passages for cooling air. To prevent this, more frequent defrosting is required. This defrosting, however, significantly increases energy consumption of the appliance. Similarly, increasing the flow velocity of the cooling air into the evaporator by, for example, increasing the fan speed not only consumes more energy but also increases the overall noise level of the appliance.
Other previous heat transfer enhancement methods have also been found to be disadvantageous when applied to refrigerators. For example, louvered or lanced fins are considered less effective than needed because of the relatively low flow velocities of cooling air in refrigerators and the frost build-up on the louvers.
Therefore, an object of the present invention is to provide an improved evaporator of more compact dimension and greater efficiency.
A further object is the provision of a refrigerator evaporator which uses less material in its construction without decreasing performance characteristics.
Another object is to provide an evaporator which minimizes the amount of refrigerant used in the refrigeration system and energy usage.
Yet another object is the provision of a tube and fin-type evaporator having improved heat transfer characteristics.